1. Field of the Invention
The present invention relates to a mechanism for lifting and lowering a magnetic head in a magnetic recording and reproducing device in which a magnetic sheet is employed as a recording medium.
2. Description of the Prior Art
Electronic photographic cameras which have recently been proposed in the art operate by reading a still image with an imaging device to convert the read image into video signals and then recording the video signals on a magnetic sheet with a magnetic recording device. The magnetic sheet stores the video signals representing one picture scene by recording them on concentric tracks. When the magnetic sheet is played back in a reproducing device, the stored video signals are reproduced so as to be observed as a visible image through an output device such as a cathoderay tube or a printer.
The magnetic recording and reproducing device of the type described above has a jacket holder for accommodating a magnetic sheet jacket with the magnetic sheet rotatably housed therein. The jacket holder is movable into a loading position of the device by placing the magnetic sheet jacket into the jacket holder and then closing a door. When the jacket holder reaches the loading position, the magnetic sheet is mounted on a motor-driven spindle and a magnetic head is brought into contact with the magnetic sheet. In the recording or playback mode, the magnetic sheet is rotated by the spindle at a high speed such as 3,600 rpm, for example, while the video signals are magnetically recorded or reproduced by the magnetic head.
For good magnetic recording and reproducing of video signals, it is necessary that the magnetic sheet and the magnetic head be stably held in contact with each other. The magnetic sheet is extremely thin, and could not stay in contact with the magnetic head if the magnetic head were simply pressed against the recording surface of the magnetic sheet. It has been customary to position a positioning plate against the back of the magnetic sheet on the opposite side from the magnetic head. The positioning plate has a groove opening toward the magnetic head so that the magnetic sheet contacting the magnetic head will be curved into the groove. Upon rotation of the magnetic sheet, the magnetic sheet is maintained in good contact with the magnetic head by the oositioning plate as well as by an air flow produced between the magnetic sheet and the positioning plate.
When no video signals are recorded on or reproduced from the magnetic sheet by the magnetic head, i.e., when the magnetic sheet is not rotated, however, the magnetic head remains held against the recording surface of the magnetic sheet. If the portion of the magnetic sheet which contacts the magnetic head should be left deformed for a long time, the contacting sheet portion will be subjected to plastic deformation. The deformed portion of the magnetic sheet will be liable to cause a recording or reproducing failure when the magnetic sheet is rotated to enable the magnetic head to record or reproduce the video signals.
One solution to the above difficulty would be to move the magnetic head vertically out of contact with the magnetic sheet when no video signals are to be recorded or reproduced while the magnetic sheet is in the loading position. Since the magnetic head is required to be kept in contact with the magnetic sheet with a high positioning accuracy, such a solution can be realized only by an arrangement which can move the lowered magnetic head upwardly to a desired position with an accuracy of a few micrometers.